Water-based acrylic emulsion dispersants utilized as grind resins for pigments and method of preparing the same

ABSTRACT

The present invention is directed to a water-based acrylic emulsion dispersant to be used as a grind resin to incorporate inorganic pigment into a pigment dispersion for a coating composition. The acrylic emulsion dispersant is the reaction product of butyl methacrylate, butyl acrylate, styrene, methyl ether polyethylene glycol methacrylate, polyethylene glycol methacrylate, and polyphosphoric acid. The present invention is also directed to a method of preparing the acrylic emulsion dispersant. In this method, the butyl methacrylate, butyl acrylate, and styrene are combined with water to establish a first reaction blend. Similarly, the methyl ether polyethylene glycol methacrylate and the polyethylene glycol methacrylate are combined with water to establish a second reaction blend. Next, the first and second reaction blends are polymerized to form an intermediate emulsion polymer containing a hydroxyl group from the functionality of the polyethylene glycol methacrylate. Finally, the hydroxyl group from the polyethylene glycol methacrylate is reacted with polyphosphoric acid to form the acrylic emulsion dispersant which is utilized for efficient wetting and grinding of the pigment.

FIELD OF THE INVENTION

[0001] The subject invention generally relates to a pigment dispersionutilized in aqueous coating compositions. More specifically, the subjectinvention relates to water-based acrylic emulsion dispersants for aninorganic pigment and a method of preparing the acrylic emulsiondispersant. BACKGROUND OF THE INVENTION

[0002] Aqueous coating compositions typically include a primary binderresin, a crosslinker, a pigment or pigments to improve the aesthetics ofthe coating composition, and other coating additives such as solvents,flow and appearance control agents, light-stabilizing additives, fillerssuch as extender pigment, and the like.

[0003] It is understood in the art that the pigment is incorporated intothe aqueous coating compositions via a pigment dispersion. The pigmentdispersion is derived from dispersion of the pigment into a grind resin.More specifically, a mill, such as a ball mill, grind mill, orcontinuous mill, is utilized to incorporate the pigment into the grindresin. The mill integrates the pigment into the grind resin until adesired particle size of the pigment is achieved, and until the pigmentis appropriately wetted by the grind resin and uniformly dispersedthroughout the grind resin.

[0004] The grind resins of the prior art have proven to be inadequatefor use as a grind resin for dispersing pigment usable in aqueouscoating compositions. The grind resins of the prior art are ineffectivebecause these resins are unable to withstand mechanical forces exertedby the mill when integrating the pigment. These grind resins are alsodeficient in wetting the pigment and in maintaining the pigmentdispersed throughout the grind resin. Instead, with the grind resins ofthe prior art, the pigment tends to coagulate or settle resulting inpoor stability and inadequate ‘shelf life’ of the pigment dispersion.

[0005] These prior art grind resins also tend to have increasedviscosities and, as understood in the art, increased viscositiestypically inhibit the amount of pigment that can be incorporated intothe grind resin. As a result, pigment dispersions that utilize the grindresins of the prior art cannot attain sufficient pigment-to-binderratios while maintaining acceptable gloss and appearance in a film ofthe coating compositions. Also, due to the increased viscosity, thesegrind resins often require solvent and other additives which increasethe overall volatile content of the pigment dispersion—a characteristicthat is undesirable throughout the coating industry.

[0006] In sum, the prior art grind resins, as detailed above, arecharacterized by one or more inadequacies. Due to the inadequaciesidentified in the prior art, it is desirable to provide water-basedacrylic emulsion dispersants to be utilized as grind resins forinorganic pigments and a method of preparing the water-based acrylicemulsions. It is advantageous that the acrylic emulsion dispersantsaccording to the subject invention effectively wet the pigments,uniformly disperse the pigments, and provide increased pigment-to-binderratios accompanied with acceptable gloss and appearance in the film ofthe coating composition.

SUMMARY OF THE INVENTION

[0007] A water-based acrylic emulsion dispersant is disclosed. Theacrylic emulsion dispersant of the subject invention is utilized as agrind resin, also referred to as a grind emulsion resin, to incorporateinorganic pigment into a pigment dispersion for aqueous coatingcompositions. This acrylic emulsion dispersant is the reaction productof an ethylenically unsaturated monomer, a vinylaromatic hydrocarbonmonomer, a non-functional polyalkylene glycol acrylate or methacrylatemonomer, a functional polyalkylene glycol acrylate or methacrylatemonomer having a hydroxyl group, and an acid having a first functionalacid group reactive with the hydroxyl group, and a second functionalacid group capable of providing an acid anion group.

[0008] A method of preparing the acrylic emulsion dispersant is alsodisclosed. According to this method, the ethylenically unsaturatedmonomer and the vinylaromatic hydrocarbon monomer are combined withwater to establish a first reaction blend. A non-functional polyalkyleneglycol acrylate or methacrylate monomer and a functional polyalkyleneglycol acrylate or methacrylate monomer having the hydroxyl group arecombined with water to establish a second reaction blend. Next, thefirst and second reaction blends are polymerized to form an intermediateemulsion polymer. The intermediate emulsion polymer contains thehydroxyl group which is then reacted with the acid to form thewater-based acrylic emulsion dispersant of the subject invention.

[0009] More specifically, the second functional acid group of the acidis neutralized with an amine before the first functional acid group ofthe acid is reacted with the hydroxyl group in the intermediate emulsionpolymer. After this neutralization, the first functional acid groupreacts with the hydroxyl group in the intermediate emulsion polymerthereby bonding the acid, having the acid anion group, with theintermediate emulsion polymer to form the acrylic emulsion dispersant.

[0010] The general object of the subject invention is to develop a grindresin that effectively wets inorganic pigments used in aqueous coatingcompositions and that is capable of resisting mechanical forcesintroduced by the mills that are used to grind and integrate theinorganic pigments into the grind resin. In resisting the mechanicalforces exerted by the mills, this grind resin is ideal in that itprovides sufficient time for the mill to achieve ideal particle sizes ofthe inorganic pigments.

[0011] It is a further object of the subject invention to develop agrind resin that has a relatively low molecular weight and acorrespondingly low viscosity such that increased pigment-to-binderratios can be achieved while maintaining a low viscosity for the pigmentdispersion. More specifically, as a result of the relatively lowviscosity of the grind resin of the subject invention, higherconcentrations of pigments can be incorporated into the grind resin toattain the increased pigment-to-binder ratios of the pigment dispersion.Due to the higher concentration of pigment, a solid, into the grindresin, the volatile content of the pigment dispersion, and of theoverall coating composition, is decreased. Also, even at the increasedpigment-to-binder ratios, this grind resin demonstrates superiordispersion stability through extended shelf life of the pigmentdispersion, and this grind resin is able to be completely dispersed intowater with little or no co-solvent required to promote dispersibility.This grind resin is also suitable for achieving optimal appearancecharacteristics, such as distinctiveness and gloss, in a film of thecoating composition.

DETAILED DESCRIPTION OF THE INVENTION

[0012] The water-based acrylic emulsion dispersant of the subjectinvention is a ‘primary’ emulsion. By the term primary emulsion, it isto be understood that the subject invention is in a uniform,water-dispersed form with water being the only medium. The acrylicemulsion dispersant is utilized as a grind resin to incorporateinorganic pigment into a pigment dispersion for aqueous coatingcompositions. Examples of inorganic pigments that are utilized inaqueous coating compositions include, among other inorganic pigments,titanium dioxide, TiO₂, and iron oxide, FeO, as well as certain aluminumand mica flake pigments. It is to be understood that the terms acrylicemulsion dispersant and grind resin will be used interchangeablythroughout the subject application. The acrylic emulsion dispersantincludes both organic and inorganic chemical structure having variousfunctionalities that promote efficient wetting of the inorganic pigmentand optimal stability of the pigment in the grind resin of the pigmentdispersion in the aqueous coating composition. These variousfunctionalities will be introduced and discussed below.

[0013] The acrylic emulsion dispersant is generally the reaction productof an ethylenically unsaturated monomer, a vinylaromatic hydrocarbonmonomer, a non-functional polyalkylene glycol acrylate or methacrylatemonomer, a functional polyalkylene glycol acrylate or methacrylatemonomer having a hydroxyl group, and an acid having a first functionalacid group reactive with the hydroxyl group, and a second functionalacid group capable of providing an acid anion group. It is to beunderstood that the terminology of an ethylenically unsaturated monomeris intended to include both one ethylenically unsaturated monomer andmore than one ethylenically unsaturated monomer. In fact, the preferredembodiment of the subject invention includes more than one ethylenicallyunsaturated monomer which will be described below.

[0014] The method of preparing the acrylic emulsion dispersant includesthe steps of combining the ethylenically unsaturated monomer and thevinylaromatic hydrocarbon monomer with water to establish a firstreaction blend, combining the non-functional polyalkylene glycolacrylate or methacrylate monomer and the functional polyalkylene glycolacrylate or methacrylate monomer having the hydroxyl group with water toestablish a second reaction blend, polymerizing the first and secondreaction blends to form an intermediate emulsion polymer containing thehydroxyl group, and reacting the hydroxyl group with the acid. Themethod steps of the subject invention are preferably conducted attemperatures between 25° C. and 100° C., more preferably between 50° C.and 100° C. This method will be described in further detail below.

[0015] The ethylenically unsaturated monomer is hydrophobic, i.e.,insoluble in water, and in preparing the acrylic emulsion dispersant ofthe subject invention, the ethylenically unsaturated monomer is selectedto promote miscibility between the acrylic emulsion dispersant and abinder resin of the aqueous coating composition. As appreciated by thoseskilled in the art, the binder resins of aqueous coating compositionsare preferably either a polyacrylic or polyester binder resin. Theethylenically unsaturated monomer is also selected to achieve an idealminimum film forming temperature, MFFT, for the acrylic emulsiondispersant, and ultimately for the film of the aqueous coatingcomposition, such that the acrylic emulsion dispersant and the film areresistant to excessive cracking and chipping. The MFFT of the acrylicemulsion dispersant is preferably 0 to 15° C., more preferably 5 to 10°.The acrylic emulsion dispersant is further selected such thatphoto-sensitivity of the acrylic emulsion dispersant and of the filmcontaining the acrylic emulsion dispersant is minimized.

[0016] The ethylenically unsaturated monomer is present in the acrylicemulsion dispersant in an amount from 5 to 30, preferably from 15 to 20,parts by weight based on 100 parts by weight of the acrylic emulsiondispersant, including water. In terms of the total monomer composition,the ethylenically unsaturated monomer is present in an amount from 30 to60, preferably from 45 to 55, parts by weight based on 100 parts byweight of total monomer composition. It is to be understood that, inaddition to the content of the ethylenically unsaturated monomer, thetotal monomer composition also includes the content of the vinylaromatichydrocarbon monomer, the non-functional polyalkylene glycol methacrylatemonomer, and the functional polyalkylene glycol methacrylate monomer,all of which will be discussed in greater detail below.

[0017] The ethylenically unsaturated monomer is more specificallyselected from the group of compounds consisting of aliphatic acrylates,aliphatic methacrylates, cycloaliphatic acrylates, cycloaliphaticmethacrylates, and mixtures thereof. It is to be understood that each ofthe compounds, the aliphatic acrylates, the aliphatic methacrylates, thecycloaliphatic acrylates, and the cycloaliphatic methacrylates, includean alkyl radical. In the preferred embodiment of the subject invention,the alkyl radicals of these compounds include up to 20 carbon atoms.When selected as an ethylenically unsaturated monomer, the aliphaticacrylates are present in an amount from 15 to 30, preferably from 23 to29, parts by weight based on 100 parts by weight of total monomercomposition. Similarly, when the aliphatic methacrylates are selected asan ethylenically unsaturated monomer, these monomers are present in anamount from 15 to 30, preferably from 23 to 29, parts by weight based on100 parts by weight of total monomer composition.

[0018] In the preferred embodiment, there is more than one type ofethylenically unsaturated monomer. The differing types of ethylenicallyunsaturated monomers are selected to balance the physicalcharacteristics of the acrylic emulsion dispersant set forth above. Thatis, more than one type of the ethylenically unsaturated monomer balancesthe MFFT and establishes the desired crack and chip resistance as wellas the desired photo-sensitivity of the acrylic emulsion dispersant, andof the film of the aqueous coating composition.

[0019] The aliphatic acrylates that may be selected as one of theethylenically unsaturated monomers are selected from the groupconsisting of methyl acrylate, ethyl acrylate, propyl acrylate, butylacrylate, hexyl acrylate, ethylhexyl acrylate, stearyl acrylate, laurylacrylate, and mixtures thereof. The aliphatic methacrylates that may beselected as one of the ethylenically unsaturated monomers are selectedfrom the group consisting of methyl methacrylate, ethyl methacrylate,propyl methacrylate, butyl methacrylate, hexyl methacrylate, ethylhexylmethacrylate, stearyl methacrylate, lauryl methacrylate, and mixturesthereof. The cycloaliphatic acrylate that may be selected as one of theethylenically unsaturated monomers is cyclohexyl acrylate, and thecycloaliphatic methacrylate that may be selected as one of theethylenically unsaturated monomers is cyclohexyl methacrylate.

[0020] In the preferred embodiment of the subject invention, there aretwo ethylenically unsaturated monomers, butyl methacrylate (BMA) andbutyl acrylate (BA). For descriptive purposes, chemical representationsof BMA and BA are respectively disclosed below.

[0021] As with the ethylenically unsaturated monomer or monomers, thevinylaromatic hydrocarbon monomer is also hydrophobic, i.e., insolublein water, and in preparing the acrylic emulsion dispersant, thevinylaromatic hydrocarbon monomer is also selected to promotemiscibility between the acrylic emulsion dispersant and the binder resinof the aqueous coating composition. The vinylaromatic hydrocarbonmonomer is also selected to establish the ideal MFFT and to control thephoto-sensitivity for the acrylic emulsion dispersant and the film.

[0022] The vinylaromatic hydrocarbon monomer is present in the acrylicemulsion dispersant in an amount from 1 to 15, preferably from 3 to 9,parts by weight based on 100 parts by weight of the acrylic emulsiondispersant, including water. In terms of the total monomer composition,the vinylaromatic hydrocarbon monomer is present in an amount from 5 to20, preferably from 10 to 15, parts by weight based on 100 parts byweight of total monomer composition. Furthermore, the molar ratio of theethylenically unsaturated monomer to the vinylaromatic hydrocarbonmonomer is from 1:1 to 10:1.

[0023] The vinylaromatic hydrocarbon monomer is more specificallyselected from the group consisting of styrene, α-methylstyrene,vinyltoluene, diphenylethylene, and mixtures thereof. In the preferredembodiment of the subject invention, the vinylaromatic hydrocarbonmonomer is styrene. For descriptive purposes, a chemical representationof styrene is disclosed below.

[0024] To prepare the acrylic emulsion dispersant, the ethylenicallyunsaturated monomer and the vinylaromatic hydrocarbon monomer arecombined with water to establish the first reaction blend. As statedabove, the ethylenically unsaturated monomers and the vinylaromatichydrocarbon monomer are insoluble in water. As such, it is alsonecessary to add an anionic surfactant to the first reaction blend suchthat the ethylenically unsaturated monomer and the vinyl aromatichydrocarbon monomer become dispersed in, and can be incorporated into,the water. Preferably, a sulfonate-based surfactant is selected as theanionic surfactant. In terms of the preferred embodiment, the BMA and BAand styrene are combined with water and the anionic surfactant toestablish the first reaction blend. In this embodiment, the molar ratioof the BMA and BA to styrene is 2.5:1.

[0025] The acrylic emulsion dispersant is also the reaction product ofthe non-functional polyalkylene glycol acrylate or methacrylate monomer.That is, it is to be understood that the acrylic emulsion dispersant maybe the reaction product of either the non-functional polyalkylene glycolacrylate monomer, or the reaction product of the non-functionalpolyalkylene glycol methacrylate monomer, and even mixtures thereof.However, as will be described in significant detail below, the acrylicemulsion dispersant is preferably the reaction product of thenon-functional polyalkylene glycol methacrylate. As such, fordescriptive purposes only, the subject invention will be described belowonly in terms of the non-functional polyalkylene glycol methacrylate andnot the non-functional polyalkylene glycol acrylate.

[0026] The non-functional polyalkylene glycol methacrylate monomer issoluble and miscible in water and is of the general formula

[0027] As shown above, the non-functional polyalkylene glycolmethacrylate monomer includes an ethoxy group (CH₂CH₂O) which promotesthe solubility and miscibility of the entire monomer in water. Theethoxy group of the non-functional polyalkylene glycol methacrylatemonomer terminates with a non-functional, i.e., un-reactive, methylgroup (CH₃). It is important that this monomer be non-functional tocontrol the viscosity of the completed acrylic emulsion dispersant. Thevariable x in the general formula of the non-functional polyalkyleneglycol methacrylate monomer can range from 5 to 50. The non-functionalpolyalkylene glycol methacrylate monomer is present in an amount from 1to 15, preferably from 4 to 7, parts by weight based on 100 parts byweight of total monomer composition.

[0028] In the preferred embodiment, the non-functional polyalkyleneglycol methacrylate monomer is methyl ether polyethylene glycolmethacrylate (MPEGMA), and x is 6 resulting in a formula weight for theMPEGMA of approximately 350 amu (atomic mass units). For descriptivepurposes, a chemical representation of the preferred non-functionalmonomer, MPEGMA, is disclosed below.

[0029] In alternative embodiments, where the non-functional polyalkyleneglycol acrylate is selected, the preferred non-functional polyalkyleneglycol acrylate is methyl ether polyethylene glycol acrylate.

[0030] The acrylic emulsion dispersant is also the reaction product ofthe functional polyalkylene glycol acrylate or methacrylate monomerhaving the hydroxyl group. That is, it is to be understood that theacrylic emulsion dispersant may be the reaction product of either thefunctional polyalkylene glycol acrylate monomer having the hydroxylgroup, or the reaction product of the functional polyalkylene glycolmethacrylate monomer having the hydroxyl group, and even mixturesthereof. However, as will be described in significant detail below, theacrylic emulsion dispersant is preferably the reaction product of thefunctional polyalkylene glycol methacrylate. As such, for descriptivepurposes only, the subject invention will be described below only interms of the functional polyalkylene glycol methacrylate and not thefunctional polyalkylene glycol acrylate.

[0031] In the context of the subject invention, the functionalpolyalkylene glycol methacrylate monomer is functional because thismonomer includes a hydroxyl group. As with the non-functionalpolyalkylene glycol methacrylate monomer, the functional polyalkyleneglycol methacrylate monomer is soluble and miscible in water. Thefunctional monomer is of the general formula

[0032] As shown above, the functional polyalkylene glycol methacrylatemonomer includes an ethoxy group (CH₂CH₂O) which promotes the solubilityand miscibility of the entire monomer in water. The ethoxy group of thefunctional polyalkylene glycol methacrylate monomer terminates with afunctional, i.e., reactive, hydrogen atom thereby establishing thehydroxyl group of the functional monomer. The significance of thisfunctional hydroxyl group will be described below. The variable y in thegeneral formula of the functional polyalkylene glycol methacrylatemonomer can range from 5 to 50. The functional polyalkylene glycolmethacrylate monomer is present in an amount from 25 to 40, preferablyfrom 27 to 30, parts by weight based on 100 parts by weight of totalmonomer composition. Furthermore, the molar ratio of the functionalpolyalkylene glycol methacrylate monomer with the hydroxyl group to thenon-functional polyalkylene glycol methacrylate monomer is from 5:1 to15:1. Of course, if the functional polyalkylene glycol acrylate monomerwith the hydroxyl group and the non-functional polyalkylene glycolacrylate monomer are used, as would be in certain alternativeembodiments, the above molar ratio, from 5:1 to 15:1 remains applicable.

[0033] The functional polyalkylene glycol methacrylate monomer isselected from the group consisting of polyethylene glycol methacrylate(PEGMA), polypropylene glycol methacrylate, and mixtures thereof. In thepreferred embodiment, the functional polyalkylene glycol methacrylatemonomer is PEGMA, and y is 7 resulting in a formula weight for the PEGMAof approximately 360 amu (atomic mass units). For descriptive purposes,a chemical representation the preferred functional monomer, PEGMA, isdisclosed below.

[0034] In alternative embodiments, where the functional polyalkyleneglycol acrylate is selected, the preferred functional polyalkyleneglycol acrylate is polyethylene glycol acrylate.

[0035] To prepare the acrylic emulsion dispersant, the non-functionalpolyalkylene glycol methacrylate monomer and the functional polyalkyleneglycol methacrylate monomer having the hydroxyl groups are combined withwater to establish the second reaction blend. Since, as stated above,both the non-functional polyalkylene glycol methacrylate monomer and thefunctional polyalkylene glycol methacrylate monomer are soluble inwater, there is no need to add any of the anionic surfactant to thesecond reaction blend. In terms the preferred embodiment, the MPEGMA andthe PEGMA are combined with water to establish the second reactionblend. In this embodiment, the molar ratio of the PEGMA to the MPEGMA is10:1.

[0036] In addition to the above, an initiator, also known as apolymerization promoter, is incorporated into the second reaction blendto initiate an emulsion polymerization process which will be describedbelow. The initiator is soluble in water and is selected from the groupof inorganic persulfates consisting of ammonium persulfate, (NH₄)₂S₂O₈,potassium persulfate, K₂S₂O₈, and sodium persulfate, Na₂S₂O₈. Of course,other suitable initiators including, but not limited to, conventionalinorganic peroxodisulfates and ammonium or alkali metalperoxydiphosphates can also be utilized to initiate the emulsionpolymerization process.

[0037] Next, the first and second reaction blends are polymerized toform an intermediate emulsion polymer. More specifically, the first andsecond reaction blends are fed into a distinct reaction flask wherepolymerization forms the intermediate emulsion polymer. The intermediateemulsion polymer contains the hydroxyl group from the functionalpolyalkylene glycol methacrylate, in the preferred embodiment PEGMA. Fordescriptive purposes, a chemical representation of the general formulaof the intermediate emulsion polymer is disclosed below.

[0038] R₁ is a polymer chain as defined above. That is, R₁ containsmonomers selected from the group consisting of ethylenically unsaturatedmonomers and vinylaromatic hydrocarbon monomers, and mixtures thereof,and the variables x and y range from 5 to 50 as described above. Thevariable p is indicative of the number of MPEGMA monomers in thecomplete polymer chain, and the variable q is indicative of the numberof PEGMA monomers in the complete polymer chain. The variables p and qrange from 1 to 100 which will be described further below.

[0039] In terms of the preferred embodiment, R₁ is specifically definedas follows:

[0040] which includes BMA, BA, and styrene, and the variables m, n, ando varying from 1 to 100. It is to be understood that the variables m, n,and o are respectively indicative of the number of BMA, BA, and styrenemonomers in the complete polymer chain. As such, the completeintermediate emulsion polymer, in terms of the preferred embodiment,appears as disclosed below.

[0041] In this preferred embodiment, the variables m, n, o, p, and qmore specifically range from 5 to 20 such that there are, on average,100 monomers per polymer chain. Of course, the number of monomers perpolymer chain drives the molecular weight of the acrylic emulsiondispersant as will be described below.

[0042] To control the extent of polymerization and thus the molecularweight during the emulsion polymerization process, the subject inventionutilizes a water-soluble, chain transfer agent. The chain transfer agentcan either be incorporated into the second reaction blend, with theMPEGMA, PEGMA, and water, or the chain transfer agent can beincorporated into the polymerization reaction flask that the first andsecond reaction blends are fed into. The chain transfer agent is amercaptan, i.e., a thiol, of the general formula R₂—SH, wherein R₂ is ahydrocarbon chain. Preferably, the mercaptan is selected from the groupconsisting of ethyl mercaptan and 2-nonanethiol, and mixtures thereof.Other suitable chain transfer agents include polyhalogen compounds. Thechain transfer agent of the subject invention controls the number ofmonomers per polymer chain such that the variables m, n, o, p, and qrange from 5 to 20 and there are, on average, 100 monomers per polymerchain.

[0043] After the intermediate emulsion polymer is formed, the acid isreacted with the hydroxyl group in the intermediate emulsion polymerfrom either the functional polyalkylene glycol acrylate or methacrylate.More specifically, it is the first functional acid group of the acidthat is reacted with the hydroxyl group. The first functional acid groupreacts with the hydroxyl group such that a bond is established betweenthe oxygen atom in the hydroxyl group of the intermediate emulsionpolymer and the acid.

[0044] However, it is preferred that prior to the reaction between thefirst functional acid group and the hydroxyl group in the intermediateemulsion polymer, the second functional acid group of the acid isneutralized with an amine such that the second functional acid groupprovides the acid anion group, O⁻. The acid anion group, as will bediscussed further below, interacts with metal centers that are inherentin inorganic pigments to anchor the pigment or pigments in the pigmentdispersion.

[0045] In view of the above requirements for the first and secondfunctional acid groups, the acid is selected from the group consistingof polyphosphoric acid, sulfuric acid, sulfurous acid, and dicarboxylicacids. Suitable dicarboxylic acids include, but are not limited to,oxalic acid, malonic acid, succinic acid, glutaric acid, and mixturesthereof.

[0046] Of course, it is to be considered equivalent that the hydroxylgroup of the intermediate emulsion polymer can alternatively be reactedwith suitable carboxylic acid anhydrides including, but not limited to,maleic anhydride, hexahydrophthalic anhydride, methyl-hexahydrophthalicanhydride, tetrahydrophthalic anhydride, phthalic anhydride, succinicanhydride, dodecenylsuccinic anhydride, trimellitic anhydride, andmixtures thereof. The ring structure in these anhydrides will open uponreaction with the hydroxyl group, and have the second functional acidgroup remaining which then can provide the acid anion group uponneutralization with the amine.

[0047] In the preferred embodiment, the acid is polyphosphoric acidwhich has three hydroxyl groups. The polyphosphoric acid is reacted withthe hydroxyl group from the functional polyalkylene glycol acrylate ormethacrylate in the intermediate emulsion polymer. However, as discussedabove, before the polyphosphoric acid of the preferred embodiment andthe intermediate emulsion polymer are reacted, the polyphosphoric acidis neutralized with the amine. The amine is reacted with thepolyphosphoric acid in a molar ratio of two moles of amine for every onemole of polyphosphoric acid. It is understood in the art thatpolyphosphoric acid includes both an H₃PO₄ chemical component and a P₂O₅chemical component. The amine is selected from the group consisting ofdimethylethanolamine and amino methyl propanol, and mixtures thereof.Preferably, the amine is dimethylethanolamine, (CH₃)₂NCH₂CH₂OH. Otheramines suitable in the subject emulsion polymerization process include,but are not limited to NH₃ and alkyl amines such as diethylamine.

[0048] For descriptive purposes, a chemical representation of the H₃PO₄chemical component of the polyphosphoric acid is disclosed below.

[0049] Specifically, two of the three hydroxyl groups of thepolyphosphoric acid function as second functional acid groups and areneutralized with the amine to provide the acid anion groups prior toreacting the hydroxyl group in the intermediate emulsion polymer withthe polyphosphoric acid. After this neutralization step, the phosphoricacid is in the following ionic form having two acid anion groups.

[0050] Next, the one hydroxyl group of the polyphosphoric acid thatremains un-neutralized by the amine, i.e., the first functional acidgroup of the polyphosphoric acid, is reacted with the hydroxyl group inthe intermediate emulsion polymer from the functional polyalkyleneglycol acrylate or methacrylate such that the bond is establishedbetween the intermediate emulsion polymer and the polyphosphoric acid toform the completed acrylic emulsion dispersant. More specifically, thebond is established between the phosphorus atom of the polyphosphoricacid and the oxygen atom from hydroxyl group of the terminal ethoxygroup in the functional polyalkylene glycol acrylate or methacrylate. Interms of the preferred embodiment, the one hydroxyl group of thepolyphosphoric acid that remains un-neutralized, i.e., the firstfunctional acid group, is reacted with the hydroxyl group in theintermediate emulsion polymer from the PEGMA. For descriptive purposes,a chemical representation of a general formula of the completed acrylicemulsion dispersant is disclosed below.

[0051] All variables are defined as above. In terms of the preferredembodiment, including the BMA, the BA, the styrene, the MPEGMA, thePEGMA, and the polyphosphoric acid, a chemical representation isdisclosed below.

[0052] Notice in this chemical representation, the completed acrylicemulsion dispersant has acid functionality, with two acid anion groups,and the preferred amine, dimethylethanolamine, remains in the reactionin cationic form.

[0053] The completed acrylic emulsion dispersant includes, on average,100 monomers and has a weight-average molecular weight, M_(w), of from10,000 to 100,000. Preferably, the molecular weight is from 10,000 to40,000, and more preferably, from 10,000 to 17,000. The completedacrylic emulsion dispersant has a number-average molecular weight,M_(n), of 10,000 or less. Additionally, the acrylic emulsion dispersantof the subject invention has a non-volatile content of from 20 to 40,preferably from 25 to 35, percent non-volatile by weight. This acrylicemulsion dispersant is also completely hydrophilic such that it can bein the uniform, water-dispersed form that is characteristic of primaryemulsions.

[0054] Pigment dispersions utilizing this acrylic emulsion dispersanthave pigment-to-binder ratios exceeding 30, preferably from 30 to 40with pigment particles having a particle size of less than six microns.That is, the grind resin of the subject invention is robust enough topermit the inorganic pigments dispersed within to be ground or milledlong enough to achieve pigment particle sizes of less than six micronswithout degradation and coagulation of the grind resin. Of course, it isto be understood that other pigment dispersions utilizing this acrylicemulsion dispersant may also have pigment-to-binder ratios less than 30.Furthermore, pigment dispersions utilizing this acrylic emulsiondispersant have viscosities of less than 80 Krebs units. The viscositiesof these pigment dispersions were measured after thirty minutes ofmixing with a Cowles blade at approximately 3000 RPM and at 75 to 85° F.

[0055] The resulting structure of the completed acrylic emulsiondispersant of the subject invention essentially ‘anchors’ the inorganicpigment in the pigment dispersion thereby maintaining the pigmentuniformly dispersed throughout the grind resin. More specifically, theacid functionality, or the acid anion groups, of the completed acrylicemulsion dispersant physically interacts with the metal centers inherentin inorganic pigments by complex or coordinated covalent bonding. Thisphysical interaction keeps the pigment uniformly dispersed throughoutthe grind resin. Also, as discussed above, the selection of monomers, inparticular the selection of the ethylenically unsaturated monomers andthe vinylaromatic hydrocarbon monomers, promotes thorough miscibilitybetween the acrylic emulsion dispersant and the binder resin of theaqueous coating composition.

[0056] It is to be understood that all of the preceding chemicalrepresentations are merely two-dimensional chemical representations andthat the structure of these chemical representations may be other thanas indicated. It is also to be understood that although the chemicalrepresentations disclosed above that relate to the structure of thepolymer chain indicate that the completed acrylic emulsion dispersanthas specific ‘blocks’ of monomers, in reality, the monomers are randomlydistributed throughout the polymer based on the molar ratios of themonomers as well as the relative reactivity realized between thediscrete monomer components.

[0057] The following examples illustrating the formation of and the useof the acrylic emulsion dispersant of the subject invention, aspresented herein, are intended to illustrate and not limit theinvention.

EXAMPLES Example 1

[0058] The acrylic emulsion dispersant was prepared by adding andreacting the following parts, by weight, unless otherwise indicated.TABLE 1 Targeted Actual Amount Amount Reactant (moles) (grams) OtherButyl Methacrylate .692 99.3 — [BMA] Butyl Acrylate .690 88.7 — [BA]Styrene .560 56.3 — [MPEGMA] .027 9.4 — [PEGMA] .278 102.2 Total MonomerComposi- tion equal to 355.9 grams (NH₄)₂S₂O₈ N/A 1.16 0.3 wt. % of theTotal [Initiator] Monomer Composition Anionic Surfactant N/A 22.7 −1.3wt. % of the Total Monomer Composition −22.7 grams of a 20% aqueoussoln. of the Anionic Surfactant (4.54 grams of Anionic Surfactant and18.16 grams of H₂O) Mercaptan N/A 7.5 2.0 wt. % of the Total MonomerComposition Water N/A 833.3 — [de-ionized water] TOTAL N/A 1220.56 —Intermediate Emulsion Polymer is formed Polyphosphoric .095 47.2 47.2grams of a 20% aque- Acid ous soln. of the Polyphos- phoric acid (10.1grams H₃PO₄ and 37.1 grams H₂O) Dimethylethanolamine .190 84.7 84.7grams of a 20% aque- [DMEA] ous soln. of the DMEA (17.1 grams DMEA and67.6 grams H₂O)

[0059] Per the above table, Table 1, 99.3 grams of BMA and 88.7 grams ofBA and 56.3 grams of styrene and 13.8 grams of anionic surfactant werecombined with 278.8 grams of water to establish the first reactionblend. 9.4 grams of MPEGMA and 102.2 grams of PEGMA and 1.16 grams ofInitiator were combined with 276.5 grams of water to establish thesecond reaction blend. Also, 7.5 grams of mercaptan were added to thesecond reaction blend. Next, a distinct polymerization reaction flaskwas prepared with 8.9 grams of Anionic Surfactant and 278.0 grams ofwater, and the first and second reaction blends were polymerized to formthe intermediate emulsion polymer in the polymerization reaction flask.More specifically, the first and second reaction blends were dual-fedinto the polymerization reaction flask, already including the AnionicSurfactant and the water, for approximately two hours to from theintermediate emulsion polymer. Throughout the two hour dual-feed, thepolymerization reaction flask was heated via a conventional heat supplyto a temperature of 80° C. After the two hour dual-feed, thepolymerization reaction flask was maintained at 80° C. for an additionaltwo hours, now totaling approximately four hours, and then the heatsupply was suspended.

[0060] Once the intermediate emulsion polymer was formed, 84.7 grams ofa 20% aqueous solution of DMEA were reacted with 47.2 grams of a 20%aqueous solution of polyphosphoric acid to neutralize two of the threehydroxyl groups of the polyphosphoric acid and form the acrylic emulsiondispersant of the subject invention. Then the neutralized polyphosphoricacid was added to the intermediate emulsion polymer in thepolymerization reaction flask to react the hydroxyl group of thepolyphosphoric acid that remained un-neutralized by the amine with thehydroxyl group in the intermediate emulsion polymer from the functionalpolyalkylene glycol methacrylate.

[0061] The completed acrylic emulsion dispersant has a pH value of 8.16at 25° C., and an acid number, determined by conventional methods, of 39indicative of the content of H₃PO₄ in the completed acrylic emulsiondispersant. Under GPC analysis, the M_(n) and M_(w) of the subjectdispersant were 4,110 and 15,330, respectively.

Example 2

[0062] The completed acrylic emulsion dispersant was then incorporatedinto a modified pigment dispersion according to the following table,Table 2. TABLE 2 Pigment Dispersion Component (modified) Amount (grams)Other ACRYLIC EMULSION DISPERSANT 211.0 — water 207.0 — [de-ionizedwater] co-solvent 48.0 — [propyl propasol] pigment 939.0 Added pigmentgradually over [titanium dioxide, TiO₂] time and under stirringdefoaming additive 0.29 — Appearance Evaluation N/A Glossy appearance ofmodified pigment dispersion on a 2 mil thickness drawdown

[0063] Per the above table, Table 2, 211.0 grams of the acrylic emulsiondispersant and 207.0 grams of de-ionized water and 48.0 grams of propylpropasol and 0.29 grams of a defoaming additive were added together toprepare a modified pigment dispersion for an aqueous coatingcomposition. Next, 939.0 grams of TiO₂ pigment were added gradually overtime and under stirring to the acrylic emulsion dispersant/thede-ionized water/propyl propasol blend.

[0064] The appearance of the modified pigment dispersion was evaluatedby a 2 mil thickness drawdown. The evaluation of the modified pigmentdispersion utilizing the acrylic emulsion dispersant of the subjectinvention concluded a glossy appearance with slight aeration.Additionally, the particle size of the modified pigment dispersion wasdetermined utilizing a standard grind gauge method. No pigment particleswere observed thereby indicating that the pigment particle size is lessthan six microns according to the standards of the grind gauge method.The pigment-to-binder ratio of this modified pigment dispersion was15.34, and this modified pigment dispersion had a viscosity of 60 Krebsunits after thirty minutes of mixing with a Cowles blade atapproximately 3001 RPM and at 75° F.

[0065] The invention has been described in an illustrative manner, andit is to be understood that the terminology which has been used isintended to be in the nature of words of description rather than oflimitation. Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings, and theinvention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A pigment dispersion comprising inorganic pigmentand a water-based acrylic emulsion dispersant comprising the reactionproduct of: an ethylenically unsaturated monomer; a vinylaromatichydrocarbon monomer; a non-functional polyalkylene glycol acrylate ormethacrylate monomer, a functional polyalkylene glycol acrylate ormethacrylate monomer having a hydroxyl group; and an acid having a firstfunctional acid group reactive with said hydroxyl group, and a secondfunctional acid group capable of providing an acid anion group.
 2. Apigment dispersion as set forth in claim 1 further comprising an aminefor neutralizing said polyphosphoric acid.
 3. A pigment dispersion asset forth in claim 1 wherein said ethylenically unsaturated monomer isselected from the group of compounds consisting of aliphatic acrylates,aliphatic methacrylates, cycloaliphatic acrylates, cycloaliphaticmethacrylates, and mixtures thereof, each of said compounds having up to20 carbon atoms in the alkyl radical.
 4. A pigment dispersion as setforth in claim 3 wherein said aliphatic acrylates are selected from thegroup consisting of methyl acrylate, ethyl acrylate, propyl acrylate,butyl acrylate, hexyl acrylate, ethylhexyl acrylate, stearyl acrylate,lauryl acrylate, and mixtures thereof.
 5. A pigment dispersion as setforth in claim 3 wherein said aliphatic methacrylates are selected fromthe group consisting of methyl methacrylate, ethyl methacrylate, propylmethacrylate, butyl methacrylate, hexyl methacrylate, ethylhexylmethacrylate, stearyl methacrylate, lauryl methacrylate, and mixturesthereof.
 6. A pigment dispersion as set forth in claim 1 wherein saidvinylaromatic hydrocarbon monomer is selected from the group consistingof styrene, α-methylstyrene, vinyltoluene, diphenylethylene, andmixtures thereof.
 7. A pigment dispersion as set forth in claim 1wherein said non-functional polyalkylene glycol methacrylate monomer isfurther defined as methyl ether polyethylene glycol methacrylate.
 8. Apigment dispersion as set forth in claim 1 wherein said functionalpolyalkylene glycol methacrylate monomer having a hydroxyl group isselected from the group consisting of polyethylene glycol methacrylate,polypropylene glycol methacrylate, and mixtures thereof.
 9. A pigmentdispersion as set forth in claim 1 wherein said acid having said firstand second functional acid groups is selected from the group consistingof polyphosphoric acid, sulfuric acid, sulfurous acid, and dicarboxylicacids.
 10. A pigment dispersion as set forth in claim 1 wherein saidacrylic emulsion dispersant has a molecular weight of from 10,000 to100,000.
 11. A pigment dispersion as set forth in claim 1 wherein saidacrylic emulsion dispersant has a non-volatile content of from 20 to 40percent non-volatile by weight.
 12. A water-based acrylic emulsiondispersant for efficient wetting and grinding of a pigment, said acrylicemulsion dispersant comprising the reaction product of: an ethylenicallyunsaturated monomer; a vinylaromatic hydrocarbon monomer; anon-functional polyalkylene glycol acrylate or methacrylate monomer, afunctional polyalkylene glycol acrylate or methacrylate monomer having ahydroxyl group; and an acid having a first functional acid groupreactive with said hydroxyl group, and a second functional acid groupcapable of providing an acid anion group.
 13. An acrylic emulsiondispersant as set forth in claim 12 further comprising an amine forneutralizing said second functional acid group to provide said acidanion group.
 14. An acrylic emulsion dispersant as set forth in claim 13wherein said amine is selected from the group consisting ofdimethylethanolamine and amino methyl propanol, and mixtures thereof.15. An acrylic emulsion dispersant as set forth in claim 12 wherein saidethylenically unsaturated monomer is present in an amount from 30 to 60parts by weight based on 100 parts by weight of total monomercomposition.
 16. An acrylic emulsion dispersant as set forth in claim 12wherein said ethylenically unsaturated monomer is selected from thegroup of compounds consisting of aliphatic acrylates, aliphaticmethacrylates, cycloaliphatic acrylates, cycloaliphatic methacrylates,and mixtures thereof, each of said compounds having up to 20 carbonatoms in the alkyl radical.
 17. An acrylic emulsion dispersant as setforth in claim 16 wherein said aliphatic acrylates are selected from thegroup consisting of methyl acrylate, ethyl acrylate, propyl acrylate,butyl acrylate, hexyl acrylate, ethylhexyl acrylate, stearyl acrylate,lauryl acrylate, and mixtures thereof.
 18. An acrylic emulsiondispersant as set forth in claim 16 wherein said aliphatic acrylates arepresent in an amount from 15 to 30 parts by weight based on 100 parts byweight of total monomer composition.
 19. An acrylic emulsion dispersantas set forth in claim 16 wherein said aliphatic methacrylates areselected from the group consisting of methyl methacrylate, ethylmethacrylate, propyl methacrylate, butyl methacrylate, hexylmethacrylate, ethylhexyl methacrylate, stearyl methacrylate, laurylmethacrylate, and mixtures thereof.
 20. An acrylic emulsion dispersantas set forth in claim 16 wherein said aliphatic methacrylates arepresent in an amount from 15 to 30 parts by weight based on 100 parts byweight of total monomer composition.
 21. An acrylic emulsion dispersantas set forth in claim 16 wherein said cycloaliphatic acrylate is furtherdefined as cyclohexyl acrylate.
 22. An acrylic emulsion dispersant asset forth in claim 16 wherein said cycloaliphatic methacrylate isfurther defined as cyclohexyl methacrylate.
 23. An acrylic emulsiondispersant as set forth in claim 12 wherein said vinylaromatichydrocarbon monomer is selected from the group consisting of styrene,α-methylstyrene, vinyltoluene, diphenylethylene, and mixtures thereof.24. An acrylic emulsion dispersant as set forth in claim 12 wherein saidvinylaromatic hydrocarbon monomer is present in an amount from 5 to 20parts by weight based on 100 parts by weight of total monomercomposition.
 25. An acrylic emulsion dispersant as set forth in claim 12wherein said non-functional polyalkylene glycol methacrylate monomer isfurther defined as methyl ether polyethylene glycol methacrylate.
 26. Anacrylic emulsion dispersant as set forth in claim 12 wherein saidnon-functional polyalkylene glycol methacrylate monomer is present in anamount from 1 to 15 parts by weight based on 100 parts by weight oftotal monomer composition.
 27. An acrylic emulsion dispersant as setforth in claim 12 wherein said non-functional polyalkylene glycolacrylate monomer is present in an amount from 1 to 15 parts by weightbased on 100 parts by weight of total monomer composition.
 28. Anacrylic emulsion dispersant as set forth in claim 12 wherein saidfunctional polyalkylene glycol methacrylate monomer having a hydroxylgroup is selected from the group consisting of polyethylene glycolmethacrylate, polypropylene glycol methacrylate, and mixtures thereof.29. An acrylic emulsion dispersant as set forth in claim 12 wherein saidfunctional polyalkylene glycol methacrylate monomer having a hydroxylgroup is present in an amount from 25 to 40 parts by weight based on 100parts by weight of total monomer composition.
 30. An acrylic emulsiondispersant as set forth in claim 12 wherein said functional polyalkyleneglycol acrylate monomer having a hydroxyl group is present in an amountfrom 25 to 40 parts by weight based on 100 parts by weight of totalmonomer composition.
 31. An acrylic emulsion dispersant as set forth inclaim 12 wherein the molar ratio of said ethylenically unsaturatedmonomer to said vinylaromatic hydrocarbon monomer is from 1:1 to 10:1.32. An acrylic emulsion dispersant as set forth in claim 12 wherein themolar ratio of said functional polyalkylene glycol methacrylate monomerhaving a hydroxyl group to said non-functional polyalkylene glycolmethacrylate monomer is from 5:1 to 15:1.
 33. An acrylic emulsiondispersant as set forth in claim 12 wherein said acid having said firstand second functional acid groups is selected from the group consistingof polyphosphoric acid, sulfuric acid, sulfurous acid, and dicarboxylicacids.
 34. An acrylic emulsion dispersant as set forth in claim 12having a molecular weight of from 10,000 to 100,000.
 35. An acrylicemulsion dispersant as set forth in claim 12 having a non-volatilecontent of from 20 to 40 percent non-volatile by weight.
 36. A method ofpreparing a water-based acrylic emulsion dispersant for efficientwetting and grinding of a pigment, said method comprising the steps of:(i) combining an ethylenically unsaturated monomer and a vinylaromatichydrocarbon monomer with water to establish a first reaction blend; (ii)combining a non-functional polyalkylene glycol acrylate or methacrylatemonomer with a functional polyalkylene glycol acrylate or methacrylatemonomer having a hydroxyl group with water to establish a secondreaction blend; (iii) polymerizing the first and second reaction blendsto form an intermediate emulsion polymer containing the hydroxyl group;and (iv) reacting the hydroxyl group with an acid having a firstfunctional acid group reactive with the hydroxyl group, and a secondfunctional acid group capable of providing an acid anion group.
 37. Amethod as set forth in claim 36 further including the step of adding ananionic surfactant to the first reaction blend such that theethylenically unsaturated monomer and the vinylaromatic hydrocarbonmonomer are soluble in the water.
 38. A method as set forth in claim 36wherein the acid having the first and second functional acid groups isselected from the group consisting of polyphosphoric acid, sulfuricacid, sulfurous acid, and dicarboxylic acids.
 39. A method as set forthin claim 36 wherein the acid having the first and second functional acidgroups is polyphosphoric acid having three hydroxyl groups.
 40. A methodas set forth in claim 39 further including the step of neutralizing twoof the three hydroxyl groups of the polyphosphoric acid with an amineprior to reacting the hydroxyl group in the intermediate emulsionpolymer with the polyphosphoric acid.
 41. A method as set forth in claim40 wherein the step of (iv) reacting the hydroxyl group with the acid isfurther defined as reacting the one hydroxyl group of the polyphosphoricacid that remains un-neutralized with the hydroxyl group in theintermediate emulsion polymer.
 42. A method as set forth in claim 36wherein steps (i) through (iv) are conducted at a temperature between25° C. and 100° C.
 43. A method as set forth in claim 36 wherein theethylenically unsaturated monomer is selected from the group ofcompounds consisting of aliphatic acrylates, aliphatic methacrylates,cycloaliphatic acrylates, cycloaliphatic methacrylates, and mixturesthereof, each of said compounds having up to 20 carbon atoms in thealkyl radical.
 44. A method as set forth in claim 43 wherein thealiphatic acrylates are selected from the group consisting of methylacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexylacrylate, ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, andmixtures thereof.
 45. A method as set forth in claim 43 wherein thealiphatic methacrylates are selected from the group consisting of methylmethacrylate, ethyl methacrylate, propyl methacrylate, butylmethacrylate, hexyl methacrylate, ethylhexyl methacrylate, stearylmethacrylate, lauryl methacrylate, and mixtures thereof.
 46. A method asset forth in claim 36 wherein the vinylaromatic hydrocarbon monomer isselected from the group consisting of styrene, α-methylstyrene,vinyltoluene, diphenylethylene, and mixtures thereof.
 47. A method asset forth in claim 36 wherein the non-functional polyalkylene glycolmethacrylate monomer is further defined as methyl ether polyethyleneglycol methacrylate.
 48. A method as set forth in claim 36 wherein thefunctional polyalkylene glycol methacrylate monomer having a hydroxylgroup is selected from the group consisting of polyethylene glycolmethacrylate, polypropylene glycol methacrylate, and mixtures thereof.49. A method as set forth in claim 36 further including the step ofneutralizing the second functional acid group of the acid with an amineto provide the acid anion group prior to reacting the hydroxyl group inthe intermediate emulsion polymer with the acid.
 50. A water-basedacrylic emulsion dispersant for efficient wetting and grinding of apigment, said acrylic emulsion dispersant being of the general formula:

wherein; R₁ is a polymer chain containing monomers selected from thegroup consisting of ethylenically unsaturated monomers and vinylaromatichydrocarbon monomers, and mixtures thereof; p and q are from 1 to 100;and x and y are from 5 to
 50. 51. An acrylic emulsion dispersant as setforth in claim 50 wherein said ethylenically unsaturated monomers areselected from the group consisting of compounds consisting of aliphaticacrylates, aliphatic methacrylates, cycloaliphatic acrylates,cycloaliphatic methacrylates, and mixtures thereof, each of saidcompounds having up to 20 carbon atoms in the alkyl radical.
 52. Anacrylic emulsion dispersant as set forth in claim 51 wherein saidaliphatic acrylates are selected from the group consisting of methylacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexylacrylate, ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, andmixtures thereof.
 53. An acrylic emulsion dispersant as set forth inclaim 51 wherein said aliphatic methacrylates are selected from thegroup consisting of methyl methacrylate, ethyl methacrylate, propylmethacrylate, butyl methacrylate, hexyl methacrylate, ethylhexylmethacrylate, stearyl methacrylate, lauryl methacrylate, and mixturesthereof.
 54. An acrylic emulsion dispersant as set forth in claim 50wherein said vinylaromatic hydrocarbon monomers are selected from thegroup consisting of styrene, α-methylstyrene, vinyltoluene,diphenylethylene, and mixtures thereof.
 55. An acrylic emulsiondispersant as set forth in claim 50 wherein R₁ is further defined as

wherein; m, n, and o are from 1 to
 100. 56. A water-based acrylicemulsion dispersant for efficient wetting and grinding of a pigment,said acrylic emulsion dispersant comprising the reaction product of: anethylenically unsaturated monomer; a vinylaromatic hydrocarbon monomer;a non-functional monomer selected from the group consisting ofnon-functional polyalkylene glycol methacrylate monomers andnon-functional polyalkylene glycol acrylate monomers; a functionalmonomer selected from the group consisting of functional polyalkyleneglycol methacrylates having a hydroxyl group and functional polyalkyleneglycol acrylate monomers having a hydroxyl group; and an acid having afirst functional acid group reactive with said hydroxyl group, and asecond functional acid group capable of providing an acid anion group.